JP4226084B2 - Method for producing ε-caprolactam - Google Patents

Description

【００３１】
表−１より、シクロヘキサノンの特定の不純物を特定量以下のものを用いることにより、ε−カプロラクタム及び副生硫安の品質を向上させることができることがわかる。
【００３２】
【発明の効果】
本発明の方法によれば、シクロヘキセンを出発原料として、高品質のε−カプロラクタムを安価に製造することが可能となり、且つ副生する硫安の品質も高いので、産業上有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing ε-caprolactam using cyclohexene as a starting material. Specifically, the present invention relates to a method for producing ε-caprolactam by Beckmann rearrangement after reacting cyclohexene with water to synthesize cyclohexanol, dehydrogenating cyclohexanol to cyclohexanone.
[0002]
[Prior art]
ε-Caprolactam is mainly produced by oximation of cyclohexanone, and Beckmann rearrangement of the produced cyclohexanone oxime. This cyclohexanone oxime is generally produced by reacting cyclohexanone and hydroxylamine.
[0003]
Conventionally, cyclohexanone, which is a raw material for producing ε-caprolactam, is produced by oxidizing cyclohexane with molecular oxygen to produce a mixture of cyclohexanol and cyclohexanone, separating cyclohexanol and cyclohexanone by distillation, and cyclohexanol is dehydrogenated. It is industrially produced by a method of making cyclohexanone by reaction, or a method of partially reducing phenol with hydrogen and producing cyclohexanone by rearrangement reaction.
[0004]
In recent years, a method of hydrating cyclohexene in the presence of a zeolitic catalyst has attracted attention as a method for industrially producing cyclohexanol. Many reports on such methods have been made since the Showa 40s, but production on an industrial scale has only recently been carried out.
[0005]
[Problems to be solved by the invention]
The method for producing cyclohexanol by hydrating cyclohexene is a cost-effective method and is one of the preferred methods for producing cyclohexanol. Therefore, it is considered industrially useful if the cyclohexanol produced by this method can be used as a raw material for producing ε-caprolactam.
[0006]
In the production of ε-caprolactam, a large amount of ammonium sulfate (ammonium sulfate) is produced as a by-product in the usual method, and the quality of this ammonium sulfate is also important. In the Beckmann rearrangement reaction of cyclohexanone oxime, fuming sulfuric acid or the like is usually used. A large amount of ammonium sulfate is produced by neutralizing the obtained ε-caprolactam sulfate with ammonia.
[0007]
Therefore, the present inventors examined the production of ε-caprolactam using the cyclohexanol obtained by the production method. Unlike ε-caprolactam produced from cyclohexanol obtained by other methods, the present inventors made a difference in quality. It became clear that there were unique problems in the manufacturing method.
[0008]
[Means for Solving the Problems]
Regarding the quality of ε-caprolactam, there are evaluation items such as PZ and VB, which are considered to be derived from impurities contained in a very small amount in ε-caprolactam. Therefore, removing this impurity is thought to improve the quality of ε-caprolactam. However, it is difficult to identify the above-mentioned impurities, it is unclear from which step in the ε-caprolactam production process the impurities originate, and further, depending on the type of impurities expected to be produced. Since it is difficult to remove the ε-caprolactam, it is important to determine which impurities in which process to focus on in order to improve the quality of ε-caprolactam.
[0009]
As a result of intensive studies on the above problems, the present inventors have found that ε-caprolactam using cyclohexene as a starting material is subjected to an oximation reaction in various production processes such as hydration, dehydrogenation, oximation, and Beckmann rearrangement. The inventors have found that the above-mentioned problems can be solved by controlling the amount of specific impurities in cyclohexanone, which is a raw material in the process, and have reached the present invention.
[0010]
That is, the gist of the present invention is that cyclohexene is hydrated, and the resulting cyclohexanol is converted to cyclohexanone by dehydrogenation reaction, and then the content of impurities according to the following gas chromatography analysis conditions is set to 0 . In the method of producing ε-caprolactam by reacting cyclohexanone with hydroxylamine to make cyclohexanone oxime after 3 % or less, and further Beckmann rearrangement .
[0011]
[Gas chromatography-analysis conditions]
(1) Column: a fused silica capillary column coated with a silicone liquid phase compound containing β-cyclodextrin 20% on the inner wall with a film thickness of 0.5 μm. (2) Column size, length 60 m × inner diameter 0.53 mm
(3) Column temperature: with an initial temperature of 75 ° C., the temperature is raised to 100 ° C. at a rate of temperature increase of 1.5 ° C./min, then held for 5 minutes, and then at a temperature increase rate of 10 ° C./min to 200 ° C. The temperature is raised until it is, and then held for 20 minutes.
(4) Detection method: Flame ionization detection method (FID)
(5) Carrier gas: helium (6) Carrier gas flow rate: The cyclohexanone peak retention time (t _R ) is adjusted to a constant flow rate so as to be (19 ± 2) minutes.
(7) Impurity content: The impurity peak detected at a retention time of (1.3 to 3.0) × t _R (min) is quantified.
[0012]
Hereinafter, the present invention will be described in detail.
In the production method of the present invention, cyclohexene and water are first reacted to form cyclohexanol. The hydration reaction of cyclohexene is usually carried out using a solid acid catalyst as a catalyst. Examples of the solid acid catalyst usually include zeolite and ion exchange resin. As the zeolite, various zeolites such as crystalline aluminosilicate, aluminometallosilicate, and metallosilicate can be used, and pentasil type aluminosilicate or metallosilicate is particularly preferable. Examples of the metal contained in the metallosilicate include metal elements such as titanium, gallium, iron, chromium, zirconium, hafnium, etc. Among them, gallium is preferable.
[0013]
The hydration reaction is performed by a generally used method such as a fluidized bed method, a stirred batch method, or a continuous method. In the case of a continuous method, both a catalyst-filled continuous flow method and a stirring tank flow method are possible. The reaction temperature is advantageously low from the standpoint of equilibrium of cyclohexene hydration and the increase of side reactions, and high from the standpoint of reaction rate. The optimum temperature varies depending on the nature of the catalyst, but is usually selected from the range of 50 to 250 ° C.
[0014]
The obtained cyclohexanol is subjected to a dehydrogenation reaction to form cyclohexanone. The dehydrogenation reaction of cyclohexanol may be any conventionally known method, but is generally performed by heating to 200 to 750 ° C. in the presence of a dehydrogenation catalyst. Examples of the dehydrogenation catalyst include copper-chromium oxide and copper-zinc oxide. This reaction is an equilibrium reaction, and the product is obtained as a mixture of cyclohexanone and cyclohexanol. Therefore, cyclohexanone and cyclohexanol are separated by distillation or the like, and the separated cyclohexanol is reused as a raw material for the dehydrogenation reaction.
[0015]
According to the present inventors' investigation, it was found that the cyclohexanone obtained by the above method contains a small amount of components that have not been noticed in the past, and these impurities significantly impair the quality of the product ε-caprolactam. did. As one of the causes, it is considered that the high boiling point impurities remaining in cyclohexanone become corresponding oximes in the oximation reaction step and exist as impurities in the product ε-caprolactam. Also, these impurities are difficult to separate and purify in cyclohexanone oxime or ε-caprolactam.
[0016]
Therefore, in the present invention, gas chromatography is used as cyclohexanone to be subjected to oximation, and the content of specific impurities estimated to be higher boiling point components than cyclohexanone measured under the above conditions is 0.3% or less, preferably 0. 0.1% or less, particularly preferably 50 ppm or less is used. Among the above impurities, a large number of impurities corresponding to tens of peaks detected at a retention time of (1.7 to 2.0) × t _R (min) contribute to the quality of the produced ε-caprolactam. Since it has a particularly great influence, it is preferable to set it to 40 ppm or less. As a method of obtaining cyclohexanone having such purity, a method of adjusting the dehydrogenation reaction conditions of cyclohexanol so that a specific impurity is a specified value or less, and a condition of distillation purification of cyclohexanone obtained by the dehydrogenation reaction are adjusted. A method is illustrated.
[0017]
The cyclohexanone thus obtained is reacted with hydroxylamine under known reaction conditions to give cyclohexanone oxime. Since hydroxylamine is not a stable compound by itself, it is used in the form of hydroxylammonium sulfate or nitrate. For example, cyclohexanone and hydroxylammonium sulfate are reacted in an aqueous solution or nonaqueous solution.
[0018]
Next, cyclohexanone oxime is converted to ε-caprolactam by Beckmann rearrangement by a known method. For example, Beckmann rearrangement in concentrated sulfuric acid or fuming sulfuric acid to make ε-caprolactam sulfate, then neutralization with alkali, Beckmann rearrangement in the gas phase or liquid phase in the presence of solid acid catalyst, liquid And a Beckmann rearrangement method in which the catalyst is uniformly dissolved in the phase. In either method, the obtained ε-caprolactam is purified by distillation, crystallization, or the like to obtain a product.
[0019]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to an Example, unless the summary is exceeded.
Quantification of specific impurities in cyclohexanone in the examples was performed by gas chromatography.
[0020]
[Gas chromatography-analysis conditions]
-Equipment: GC-14A manufactured by Shimadzu Corporation
Column: WAX β-DEX 110 (fused silica capillary column coated with a silicone liquid phase compound containing 20% β-cyclodextrin on the inner wall with a film thickness of 0.5 μm), length 60 m × inner diameter 0. 53 m. Column temperature: Initial temperature 75 ° C., heated to 100 ° C. at a heating rate of 1.5 ° C./min, then held for 5 minutes, then 200 ° C. at a heating rate of 10 ° C./min. Until the temperature rises to 20 minutes.
[0021]
・ Detection method: Flame ionization detection method (FID)
Carrier gas: Helium Carrier gas flow rate: As a result of adjusting the retention time (t _R ) of cyclohexanone peak to a constant flow rate of (19 ± 1) minutes, supply pressure 140 KPa, septum purge flow rate 14 ml / min, split The flow rate was set to 28 ml / min.
・ Inlet temperature: 220 ° C
-Detector temperature: 240 ° C
Sample injection volume: 0.2 μl
Impurity quantification method: The amount of impurities in terms of cyclohexanone was determined from the peak area of impurities detected at a retention time of (1.3 to 3.0) × t _R (minutes).
In gas chromatography, there is no problem as long as the internal standard substance has a good resolution, and n-tetradecane or the like can be used. The impurity quantification method may be measured based on the peak height of the impurity.
[0022]
Comparative Example 1
(1) Hydration reaction of cyclohexene Gallium silicate (Si / Ga atomic ratio = 25/1) was used as a hydration catalyst. An autoclave equipped with a stirring blade was charged with 15 parts by weight of cyclohexene, 30 parts by weight of water, and 10 parts by weight of a hydration catalyst, and the mixture was allowed to react at 120 ° C. for 1 hour.
(2) Purification of cyclohexanol The cyclohexanol mixture obtained above was purified by a 10-stage rectification column to obtain purified cyclohexanol having a purity of 99.9%.
[0023]
(3) Dehydrogenation reaction of cyclohexanol A reaction pressure of 0.17 MPa (0.7 kg / cm ² G), LHSV was added to a tubular reactor filled with a copper-zinc catalyst that was vaporized from purified cyclohexanol and set at 250 ° C. (Liquid space velocity) The dehydrogenation reaction was carried out at 2.4 hr ⁻¹ . The yield of cyclohexanone was 60%.
(4) Purification of cyclohexanone Cyclohexanone was purified by distillation at a reflux ratio of 30 in a 30-stage rectifying column to remove low-boiling components, and then cyclohexanol was removed in a 40-stage rectifying tower. . To the obtained purified cyclohexanone, the above impurities are added, and the total impurity amount is 0.4% (impurity detected at a retention time of (1.7-2) × t _R (min) is 60 ppm) did.
[0024]
(5) Production of cyclohexanone oxime A 45% hydroxylamine sulfate aqueous solution charged in a jacketed stirring tank was heated to 85 ° C., and the cyclohexanone was added dropwise. At this time, aqueous ammonia was added dropwise so that the pH of the reaction solution was 4.0 to 4.5. After the addition of cyclohexanone was completed, stirring was continued for 30 minutes in order to complete the reaction, and the oil phase was collected as cyclohexanone oxime by standing and separating. Water contained in cyclohexanone oxime was dehydrated under reduced pressure.
[0025]
(6) Beckmann rearrangement Cyclohexanone oxime so that the acidity of the Beckmann rearrangement solution is 57% and the free SO ₃ concentration is 7.5%, and the residence time in the reactor is 1 hour. And 25% fuming sulfuric acid (orium) were simultaneously dropped into a jacketed stirring tank. At this time, in order to suppress local heat generation, stirring was performed at a stirring speed of 100 rpm or more, and cooling water was supplied to the jacket to maintain the reaction temperature at 70 to 100 ° C.
(7) SO ₃ treatment The Beckmann rearrangement liquid thus obtained was transferred to a jacketed stirring tank (500 ml), the SO ₃ concentration was maintained at 7.0 to 7.5%, and stirring was performed at a stirring speed of 300 rpm or more. 2 hours at a treatment temperature of 90 to 125 ° C., to obtain a SO ₃ treatment liquid.
[0026]
(8) Post treatment The obtained SO3 treatment solution was neutralized with aqueous ammonia. The neutralization reaction was carried out by passing warm water through a jacketed stirring tank at a neutralization temperature of 70 ° C. and a pH of 7.0 to 7.5.
Subsequently, the neutralized solution was extracted with benzene. For extraction, the neutralizing solution and benzene were placed in a separatory funnel, shaken for 10 minutes, allowed to stand for 5 minutes, and only the oil phase was collected. The aqueous phase was extracted again with benzene. At this time, the amount of benzene used was adjusted such that the theoretical amount of ε-caprolactam concentration was 18% by weight. In this way, extraction with benzene was performed three times in total, and then benzene was distilled off by a conventional method to obtain crude ε-caprolactam.
Finally, the crude ε-caprolactam was purified by distillation. Distillation is performed by adding an appropriate amount of 25% aqueous sodium hydroxide solution to crude ε-caprolactam, and then collecting it in three parts, 10% by weight of the initial fraction, 80% by weight of the main fraction, and 10% by weight of the remainder of the kettle. The target of.
[0027]
(9) Quality evaluation method of ε-caprolactam and by-product ammonium sulfate The quality of the obtained purified ε-caprolactam and by-product ammonium sulfate was evaluated with respect to the following two standards. The results are shown in Table-1.
PZ (potassium permanganate value)
1 g of ε-caprolactam sample is dissolved in 100 ml of water, and 1 ml of 0.01N potassium permanganate aqueous solution is added to it and stirred, and then a comparative standard solution (3.0 g of cobalt chloride (CoCl ₂ · 6H ₂ O) and copper sulfate Time until the same color as (CuSO ₄ .5H ₂ O) (2.00 g diluted with water to 1000 ml).
The pH of the extraction residue (aqueous phase = ammonium sulfate water) in the extraction with ammonium sulfate quality benzene is adjusted to 5.2 with 8M sulfuric acid. Dilute 5 ml of the prepared sample to 500 ml. The absorbance of this diluted solution is measured. Wavelength: 255 nm, 10 mm cell Target: Demineralized ammonium sulfate quality = absorbance (Abs) × dilution rate
Example 1
Comparison was made except that the amount of impurities added was changed to cyclohexanone having a total impurity amount of 0.2% (the retention time was (1.7-2) × t _R (min) was 20 ppm). The quality of the product caprolactam and by-product ammonium sulfate was evaluated in the same manner as in Example 1. The results are shown in Table-1.
[0029]
Example 2
The product caprolactam and by-product ammonium sulfate were added in the same manner as in Comparative Example 1 except that the impurities were not added and the cyclohexanone was further purified in a 50-stage plate-type rectification column at a reflux ratio of 30. Quality was evaluated. The results are shown in Table-1. At this time, the amount of impurities in cyclohexanone was below the detection limit (1 ppm).
[0030]
[Table 1]
Table-1

[0031]
From Table 1, it can be seen that the quality of ε-caprolactam and by-product ammonium sulfate can be improved by using a specific impurity of cyclohexanone below a specific amount.
[0032]
【The invention's effect】
According to the method of the present invention, high-quality ε-caprolactam can be produced at low cost using cyclohexene as a starting material, and the quality of by-product ammonium sulfate is high, which is industrially useful.

Claims (1)

Cyclohexene is hydrated, and the resulting cyclohexanol is converted to cyclohexanone by dehydrogenation. The content of impurities under the following gas chromatography analysis conditions is reduced to 0.3% or less, and then the cyclohexanone is reacted with hydroxylamine. A method for producing ε-caprolactam by making cyclohexanone oxime and further Beckmann rearrangement.
[Gas chromatography analysis conditions]
(1) Column: A fused silica capillary column coated with a silicone liquid phase compound containing 20% β-cyclodextrin on the inner wall with a film thickness of 0.5 μm. (2) Column size, length 60 m × inner diameter 0.53 mm (3 ) Column temperature: With an initial temperature of 75 ° C., the temperature is raised to 100 ° C. at a rate of temperature increase of 1.5 ° C./min, then held for 5 minutes, and then to 200 ° C. at a rate of temperature increase of 10 ° C./min The temperature is raised and then held for 20 minutes.
(4) Detection method: Flame ionization detection method (FID)
(5) Carrier gas: helium (6) Carrier gas flow rate: The cyclohexanone peak retention time (t _R ) is adjusted to a constant flow rate so as to be (19 ± 2) minutes.
(7) Impurity content: The impurity peak detected at a retention time of (1.3 to 3.0) × t _R (min) is quantified.